What does the Greek "E"-like symbol mean?
By Andrew Adams •
I have a simple question: what does the following mean?
$$\displaystyle\sum_{k=0}^n$$
$\endgroup$ 71 Answer
$\begingroup$This symbol is a Greek letter called (capital) sigma. It's used to denote sums. The definition is
$$ \sum_{i=1}^n a_i = a_1+\cdots+a_n. $$
For example: $$ \sum_{i=1}^6 1 = \underbrace{1+\cdots+1}_{\text{6 times}} = 6 $$
or $$ \sum_{i=1}^4 i = 1 + 2 +3+4 = 10. $$
$\endgroup$ 1
